Imaging system with optimized extended depth of focus

ABSTRACT

An optical processor is presented for applying optical processing to a light field passing through a predetermined imaging lens unit. The optical processor comprises a pattern in the form of spaced apart regions of different optical properties. The pattern is configured to define a phase coder, and a dispersion profile coder. The phase coder affects profiles of Through Focus Modulation Transfer Function (TFMTF) for different wavelength components of the light field in accordance with a predetermined profile of an extended depth of focusing to be obtained by the imaging lens unit. The dispersion profile coder is configured in accordance with the imaging lens unit and the predetermined profile of the extended depth of focusing to provide a predetermined overlapping between said TFMTF profiles within said predetermined profile of the extended depth of focusing.

This application is a continuation of U.S. patent application Ser. No.13/578,184, which has a 371(c) date of Oct. 23, 2012, the entirecontents of which are incorporated herein by reference. U.S. patentapplication Ser. No. 13/578,184 is a 371 national stage of InternationalApplication No. PCT/IL2011/000143 filed Feb. 9, 2011, which is acontinuation of U.S. patent application Ser. No. 12/781,428 filed May17, 2010, now U.S. Pat. No. 8,531,783, which International ApplicationNo. PCT/IL2011/000143 claims the benefit of U.S. Provisional PatentApplication No. 61/302,588 filed Feb. 9, 2010.

FIELD OF THE INVENTION

This invention relates to an imaging system and method for imaging withextended depth of focus.

BACKGROUND OF THE INVENTION

Extension of the depth of focus of imaging is a common goal of variousimaging systems. Techniques for extending the depth of focus of imagingsystems have been developed, and are described for example in thefollowing publications:

U.S. Pat. No. 6,536,898 and U.S. Pat. No. 7,025,454 disclose extendeddepth of field optics for human eye. This technique utilizesmodification of contact lenses, intraocular implants, and/or the surfaceof the eye itself. This is accomplished by applying selected phasevariations to these optical elements (e.g., by varying surface thicknessof the cornea of the eye). The phase variations EDF-code the wavefrontand cause the optical transfer function to remain essentially constantwithin a range of distances from the in-focus position. This provides acoded image on the retina. The human brain decodes this coded image,resulting in an in-focus image over an increased depth of field.

US 2009/0279189 describes a lens having extended depth of focus. Thelens includes a plurality of lens layers, each lens layer beingaxi-symmetric and having an extended depth of focus to focus light in acorresponding section of a focal curve in the form of a straight linelocated on an optical axis. In the optical system, light is focused onan optical axis to obtain a clear image in a wide distance range betweena camera and an object. The optical system has a point spread functionthat is simpler and more symmetric. That is, the optical system providesimproved continuity of a lens surface and easiness and flexibility inoptical designing.

U.S. Pat. Nos. 7,365,917, 7,061,693, WO 07/141788, all assigned to theassignee of the present application, describe all-optical techniques forextending the depth of focus being thus suitable for use in ophthalmicapplications. According to these techniques, an imaging arrangementcomprises an imaging lens having a certain affective aperture, and anoptical element associated with said imaging lens. The optical elementis configured as a phase-affecting, substantially non-diffractiveoptical element defining a spatially low frequency phase transition. Theoptical element and the imaging lens define a predetermined patternformed by spaced-apart substantially optically transparent features ofdifferent optical properties.

GENERAL DESCRIPTION

The present invention provides a novel all-optical technique forappropriately extended depth of focus (EDOF) of an imaging lens unit.This technique utilizes a novel coding mechanism for coding a lightfield in the vicinity of an imaging lens unit. The present inventiontakes advantage of the earlier technique developed by the inventors anddisclosed for example in the above-indicated patent publications U.S.Pat. Nos. 7,365,917, 7,061,693, WO 07/141788.

The main idea of the present invention is based on the understanding ofthe following: Imaging systems, such as human eye, have a depth of focus(DOF) determined by a number of physical parameters such as F/#,illumination spectrum and the aberrations terms (deviations from idealimaging). For an aberration-free system, the DOF could be defined asfollows (using Rayleigh 1/4 wave rule of thumb):DOF=4λF/# ²where F/#=D/EFL, EFL being the system effective focal length; and D isthe system clear aperture.

Therefore, in order to extend the DOF of such an imaging system, theaperture of the imaging system is usually reduced, unavoidably resultingin the lost of energy and resolution. EDOF technology, developed by theinventors, utilizes phase-only coding (e.g. phase mask), having largespatial features (i.e. low spatial frequency phase transitions), locatedin the imaging system entrance pupil/aperture or plane/exit pupil inorder to extend the DOF without reducing the aperture, i.e. causingneither loss of energy, nor loss of resolution. This techniqueeliminates a need for any image processing in order to restore theimage.

Phase coding of the effective aperture of an imaging lens unit forextending the depth of focus of the lens unit results in a total profileof Through Focus Modulation Transfer Function (TFMTF) different fromthat of the original imaging lens unit, i.e. with no phase coding.Further details of lenses providing phase coding are given in the aboveindicated patents U.S. Pat. Nos. 7,061,693 and U.S. Pat. No. 7,365,917assigned to the assignee of the present application, which areincorporated herein by reference in their entirety.

The inventors have found that the TFMTF profile defined by theEDOF-based phase coded imaging lens unit can be further optimized toobtain such a TFMTF profile, in which the TFMTF plot componentscorresponding to the desirably extended depth of focus for differentwavelengths (wavelength ranges) overlap in the optimal way. Theoptimization comprises applying additional coding to the light field inthe vicinity of the phase coded effective aperture of the imaging lensunit selected to take into account the EDOF effect to be obtained by thephase coding within the imaging lens unit, e.g. continuous range EDOF ordiscrete multi-range EDOF, and to compensate for longitudinal chromaticaberrations (LCA) of such EDOF imaging lens unit.

The LCA cause a shift in the extended focal position for differentwavelengths, and could thus smear the performance of the EDOF-equippedimaging system. The invention provides for compensating for LCA effectwhile extending the depth of focusing of the imaging lens unit. To thisend, the invention utilizes a dispersion profile coding (chromaticaberrations correction) of the light field which has been or is to bephase coded to thereby provide imaging with the desired profile ofextended depth of focus for multiple wavelengths where the wavelengths'TFMTF profiles are desirably overlapping within the EDOF profile. Theterm “compensating for LCA” as used herein means reducing LCA for a lensrelative to the same lens exclusive of the dispersion profile coding.

Thus, the present invention in its one broad aspect provides anall-optical processor for applying to a light field passing through apredetermined imaging lens unit, said optical processor comprising apattern in the form of spaced apart regions of different opticalproperties, said pattern being configured to define: a phase coderaffecting Through Focus Modulation Transfer Function profiles fordifferent wavelength components of said light field in accordance with apredetermined profile of an extended depth of focusing of said lightfield passing through the imaging lens unit; and a dispersion profilecoder configured to provide a predetermined overlapping between saidprofiles of the Through Focus Modulation Transfer Functions within saidpredetermined profile of the extended depth of focusing.

It should be noted that the present invention is not limited to“transmission mode” applications (such as ophthalmic applications), butis at the same time applicable to “reflective mode” imaging systems. Inother words, the object and imaging planes may be located at the sameside or at the opposite sides of the imaging lens unit. Accordingly, theterm “imaging lens unit” should be interpreted broader than just one ormore lenses, but also mirror or lens with reflective coating. Also, theterm “TFMTF” should be referred to as through focus modulation transferfunction.

The phase coder is implemented as a first pattern formed by apredetermined number of phase transitions, the phase transition being aregion affecting a phase of light differently from that of itssurroundings, while being substantially of the same transparency. Thephase transition regions are arranged with a low spatial frequencywithin the lens aperture, so as to induce substantially non-diffractivephase effect onto the light field passing therethrough.

The dispersion profile coder is implemented as a second pattern,defining an arrangement of features such that this second pattern issubstantially diffractive, and is configured to provide a predeterminedoptical power addition to the imaging lens unit. The optical power ofthe chromatic aberrations corrector (dispersion profile coder) isselected such that an imaging lens arrangement formed by saidpredetermined imaging lens unit, said phase coder and said dispersionprofile coder is characterized by a desired dispersion profile.

In one embodiment of the invention, the first and second patterns arelocated at front and rear surfaces of the imaging lens unit, withrespect to light propagation direction through the imaging lens unit.For example, the first and second patterns may be in the form of firstand second surface reliefs on said front and rear surfaces of theimaging lens unit, respectively. According to another example, these maybe phase mask and diffractive element located at the surface of the lensunit at a certain distances therefrom up to a physical contact. In yetanother example, the first and second patterns may be incorporated inthe lens unit, for example the phase coder pattern being formed byspaced-apart regions of a material having a refractive index differentfrom that of the lens unit, and the dispersion profile coder being adiffractive pattern on one of the surfaces of the lens unit.

In another embodiment, the first and second patterns are configured as asurface relief on the same surface of the lens unit.

Thus, the first and second patterns may be defined by phase anddiffractive masks associated with the lens unit, i.e. located at thesame of opposites sides of the lens unit, or incorporated in the lensunit, or defining together a combined diffractive pattern comprising asuperposition of said first and second patterns and being carried by theimaging lens unit.

According to another broad aspect of the invention, there is providedoptical processor for processing light passing therethrough, comprising:an imaging lens unit providing optical power; a non-diffractive phasecoder comprising an optical element that includes a pattern of spacedapart regions, said pattern being configured to affect a phase of lightpassing therethrough while substantially not effecting light diffractionand to provide an extended depth of focus for said lens, the imaginglens unit and said optical element being characterized by a ThroughFocus Modulation Transfer Function (TFMTF) for each of a plurality ofdifferent wavelength components of a light field passing therethrough;and a diffractive dispersion profile coder adapted to provide areduction of chromatic aberration whereby there is greater overlapbetween the TFMTFs for the plurality of different wavelength componentswithin the extended depth of focus.

The optical element and the dispersion profile coder may be disposed onthe front and rear surfaces of the lens, respectively, or on the samesurface of the imaging lens unit. At least one of the optical elementand the dispersion profile coder may be incorporated in the imaging lensunit or an element of the imaging lens unit; or at least one of theoptical element and the dispersion profile coder may be disposed at alocation separated from the imaging lens unit or an element of theimaging lens unit. Yet another option is to combine the optical elementand the dispersion profile coder as a superposition of a non-diffractivephase-affecting pattern of said optical element and a diffractivedispersion profile coder.

According to yet another broad aspect of the invention, there isprovided an imaging lens carrying an optical processor adapted forextending the depth of focus with a predetermined dispersion profile.

The invention, in its yet further broad aspect, provides an imaging lensarrangement comprising an imaging lens unit and an optical processorassociated with said imaging lens unit, the optical processor comprisinga pattern of spaced-apart regions of different optical properties, saidpattern comprising a phase coder affecting profiles of Through FocusModulation Transfer Function (TFMTF) for different wavelength componentsof a light field being imaged in accordance with a predetermined profileof an extended depth of focusing to be obtained by said imaging lensarrangement; and a dispersion profile coder configured in accordancewith the said imaging lens unit and said predetermined profile of theextended depth of focusing to provide a predetermined overlappingbetween said TFMTF profiles within said predetermined profile of theextended depth of focusing.

According to yet further broad aspect of the invention, there isprovided an imaging lens comprising a pattern of spaced-apart regions ofdifferent optical properties, said pattern comprising a phase coderaffecting profiles of Through Focus Modulation Transfer Function (TFMTF)for different wavelength components of a light field being imaged inaccordance with a predetermined profile of an extended depth of focusingto be obtained by said imaging lens arrangement; and a dispersionprofile coder configured in accordance with the said imaging lens unitand said predetermined profile of the extended depth of focusing toprovide a predetermined overlapping between said TFMTF profiles withinsaid predetermined profile of the extended depth of focusing.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, embodiments will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIGS. 1A to 1D illustrate dispersion effects in an imaging lens: FIGS.1A and 1B show the TFMTF graphs for different wavelengths (FIG. 1A) anda total TFMTF (FIG. 1B) for a single or multi-focal lens, and FIGS. 1Cand 1D show similar graphs for a bi-focal lens;

FIG. 2A shows schematically an imaging lens arrangement of the presentinvention;

FIG. 2B shows a specific example of the implementation of the imagingarrangement of FIG. 2A;

FIGS. 3A-3C exemplify the light field coding technique of the invention:FIG. 3A exemplifies an EDOF phase coding pattern, FIG. 3B exemplifiesthe dispersion profile coding pattern, and FIG. 3C shows a combinedcoding (pattern) applied to the light field propagating in the imaginglens arrangement; and

FIGS. 4A to 4D show simulation results for the TFMTF of the imaging lensarrangements of the present invention: FIGS. 4A and 4B show respectivelythe dispersion of the TFMTF profiles for different wavelengths and thetotal TFMTF for a single- or multi-focal imaging lens and FIGS. 4C and4D show similar graphs for a bifocal imaging lens.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is made to FIGS. 1A to 1D illustrating dispersion occurring inan imaging lens unit utilizing EDOF phase coding. The imaging lens unitmay comprise a single-focus or multi-focus lens (FIGS. 1A and 1B) or abi-focal lens (FIGS. 1C and 1D).

FIGS. 1A and 1C show the simulation results for a Through FocusModulation Transfer Function (TFMTF) for 100 cyc/mm spatial frequency.This simulation was carried out with Zemax, using “Arizona Eye model”,for a lens with a focal length of 16.7 mm and entrance pupil diameter of3 mm.

In FIG. 1A, four TFMTF graphs are shown, G₁-G₄, corresponding to fourdifferent wavelengths in the range 0.5-0.6 μm. As shown, there is arelative shift for each wavelength: the plot for wavelength 0.6 μm isshifted 0.18 mm away from the corresponding graph for wavelength of 0.5μm. In FIG. 1C, five TFMTF graphs R₁-R₅ are shown corresponding topassage of light of five different wavelengths in the range of 0.47-0.63μm through a diffractive bi-focal lens unit. This graphs show TFMTF,being modulus of the OTF (i.e. imaging contrast) as a function of focusshift of the lens. Assuming all wavelengths are weighted the same (areof the same intensity), the resulted plots are illustrated in FIGS. 1Band 1D respectively.

Thus, for a given value of the TFMTF, the actual obtainable depth offocus (i.e. providing sufficient contrast of the image) is smaller thanthat for each wavelength. For example, for TFMTF=0.2, about 6 mm focaldepth is obtained for each wavelength (FIG. 1A), while being about 4 mmfor the total TFMTF plot (FIG. 1B).

Hence, there is a need to compensate the dispersion such as to cause theTFMTF plots overlap in the optimal way. It should be understood that theoptimal way of overlapping means overlap within the required depth offocus region(s), defined by the specific applications. This may be onecontinuous region, or dual- or multi-region depth of focus as forexample required in some ophthalmic applications or for imagersrequiring improved image quality in the near and far vision zones.

The required compensation should take into account that DOF extensionsfor different wavelengths are different, i.e. larger for longerwavelength and smaller for shorter one, and should also take intoaccount the initial depth of focus requirements with respect to aspecific imaging lens unit. In other words, the chromatic aberrationscorrection (dispersion profile coding) should be configured inaccordance with the depth of focus profiles, of the imaging lens withthe EDOF effect, for the multiple wavelengths, e.g. those of the primarycolors.

The present invention solves the above problem by providing anall-optical processor to be applied to a light field incident onto apredetermined imaging lens unit (e.g. passing through the lens unit).This optical processing is implemented by passing light through apattern of spaced apart regions of different optical properties. Thispattern defines a phase coder affecting TFMTF profiles for differentwavelength components in accordance with predetermined EDOF profiles forcertain imaging lens unit, and also defines a dispersion profile coderconfigured to provide a predetermined overlapping between the TFMTFprofiles within the EDOF profile.

Reference is made to FIG. 2A showing schematically an imagingarrangement 10 of the present invention. The imaging arrangement 10includes an imaging lens unit 12 and an optical processor 14. Theimaging lens unit 12 may include one or more optical elements configuredand operable to create an image of an object in an imaging plane. Theoptical processor 14 may be a separate unit located close to (up tophysical contact with) the imaging lens unit 12 (generally located so asto be in the vicinity of the effective aperture of the lens unit)located at either sides of the lens unit or both of them; or may be atleast partially incorporated within the lens unit (embedded therein).The optical processor is configured to provide a desired profile of theextended depth of focus for the given imaging lens unit and a desiredTFMTF profiles of multiple wavelengths within said profile of theextended depth of focus.

As shown in FIG. 2A, the optical processor 14 includes a phase coder(mask) 16 defined by a first pattern PC, and a dispersion profile coder18 (e.g. mask) defined by a second pattern DC. In this example, themasks 16 and 18 are shown as being separate elements both separated fromthe lens unit, the phase coding mask 16 being located upstream of thelens unit and the dispersion coding mask 18 being located downstream ofthe lens with respect to the light propagation direction. It shouldhowever be noted that for the purposes of the invention the lens 12 andthe coders 16, 18 may be arranged differently. Also, the codes of masks16 and 18 may be integrated in a single pattern (mask) being separatedfrom the lens or being integral therewith (e.g. embedded therein).

It should be understood that the imaging arrangement 10 is configuredwith one or more optical powers, to provide predetermined extensionprofile for the focus (focii) defined by said optical power, and to havea desired chromatic dispersion profile. The phase coder is configured toprovide said predetermined extension profile, while substantially notadding any optical power to the lens unit. The desired optical power ofthe entire imaging arrangement for each wavelength is a sum of therespective optical powers of the elements of such arrangement. Thedispersion coder is thus configured with a certain optical power (foreach wavelength) selected such that the dispersion coder providesdesirable shifts of the TFMTFs within the predetermined depth of focusextension profile. It should be understood that desired TFMTFs may bemulti-lobe functions. Accordingly, for the given imaging lens with EDOFassembly, different dispersion codings might be used in order to achievethe desired overlap between different wavelength lobes.

FIG. 2B illustrates schematically an imaging arrangement 100 accordingto an example of the invention. The same reference numbers identifycomponents common in all examples. The imaging arrangement 100 includesan imaging lens unit 12 (formed by a single lens in the presentexample), and an optical processor 14 which is carried by opposite sides12A and 12B of the lens unit. Here, the phase and dispersion coders(patterns PC and DC) are implemented as surface patterns on the lensunit rear and front surfaces 12A and 12B. One of these patterns or bothmay be in the form of a surface relief; or may be formed by spaced-apartregions of a material having refractive index different from that of thelens.

Reference is made to FIGS. 3A-3C exemplifying the effect of the opticalprocessor according to the light field coding technique of theinvention. FIG. 3A exemplifies a radial profile of the EDOF phase codingpattern PC (mask), which is a phase only, substantially not diffractivepattern designed to provide a desired EDOF profile for the imaging lensunit. FIG. 3B exemplifies a radial profile of the dispersion profilecoding pattern DC, which is a diffractive pattern designed in accordancewith the imaging lens with the EDOF profile to desirably shift the EDOFcomponents of different wavelengths within said desired profile. FIG. 3Cshows a combined coding (pattern) applied to the light field propagatingin the imaging lens arrangement.

Let us consider the above coding of the imaging lens unit similar tothat of the example of FIGS. 1A-1B. The function of the chromaticaberrations corrector (dispersion profile coder), configured forproperly shifting the EDOF TFMTF plots, is implemented by a diffractiveelement (e.g. Fresnel lens).

Diffractive lens focal length, f_(Diff), has the following wavelengthdependency:

$f_{Diff} = \frac{\lambda_{0}f_{0}}{\lambda}$$P_{Diff} = {\frac{1}{f_{Diff}} = \frac{\lambda}{\lambda_{0}f_{0}}}$where f₀ is the focal length for a central wavelength λ₀.

FIG. 4A shows that application of the appropriately designed diffractionpattern to the EDOF imaging lens provides that the TFMTFs for multiplewavelength are well co-aligned (generally desirably overlap), giving adesired total TFMTF. The latter is shown in FIG. 4B.

The diffractive lens 18 used for dispersion profile coding was simulatedas made of PMMA material with total thickness, T_(thick), determined as:

${Tthick} = \frac{\lambda}{n_{pmma} - n_{air}}$n_(pmma) and n_(air) being respective refractive indices. The opticalpower of such diffractive lens is determined as that of refractiveplano-convex lens having power, and in the present example is:

${Pdiff} = {\frac{\left( {n_{pmma} - n_{air}} \right)}{R} = {3.33{Diopt}}}$where R=150 mm is the radius of the plano-convex refractive lenscarrying the above described diffractive pattern. In this example, thediffractive lens is configured for ophthalmic application consideringthe optical power of the eye lens.

FIGS. 4C and 4D show similar simulation results for the bi-focal lenswhere an EDOF pattern was added to the bi-focal diffractive lens. As canbe seen from the figures, the depth of focus is extended around eachfocus of the diffractive bifocal lens (attached to eye model) relativeto the narrow depth of focus seen in FIGS. 1C and 1D.

Lenses as described herein can be used in ophthalmic applications, as abeing a spectacles lens or a lens embodied as any suitable ophthalmiclens. The term “ophthalmic lens” refers to an artificial lens for usewith the eye. Preferred ophthalmic lenses are made of biomedicalmaterials suitable for contact with eye tissue. The term “ophthalmiclens” includes but is not limited to intraocular lenses (IOLs), contactlenses, and corneal onlays or inlays (intracorneal lenses).

It will be appreciated that non-optical components may be added in someembodiments of ophthalmic lenses (e.g., in intraocular lenses, one ormore haptics may be added). Lenses according to aspects of the presentinvention can comprise combinations of surfaces having any suitableshape (piano, convex, concave). The illustrated embodiments of lenseshave only one zone; however, other embodiments may have multiple zones,the zones having different optical powers.

In some embodiments, the lenses may be embodied as intraocular lensesadapted to provide accommodative movement. For example, a lens accordingto aspects of the present invention can be used in a dual elementaccommodative lens as described in U.S. Pat. No. 6,488,708 issued Dec.4, 2002, to Sarfarazi, or a single element accommodative lens asdescribed in U.S. Pat. No. 5,674,282, issued Sep. 7, 1997, to Cumming.

A pattern may be placed on a surface of the lens by various techniquesknown in the art. As a first example, the pattern may be lathe cut,lased or etched directly into the lens surface. As a second example, thepattern may be provided on a mold having a molding surface for formingthe lens surface, wherein the pattern is transferred to the mold duringcasting of the lens. For example, a conventional manner of makingcontact lenses involves casting a mixture of lens-forming monomers in atwo-part plastic mold. One mold part includes a molding surface forforming the front lens surface, and the second mold part includes amolding surface for forming the back lens surface. The monomer mixtureis polymerized, or cured, while in the two-part mold to form a contactlens. The plastic mold parts are injected molded from a metal tool. Forsuch a method, the pattern may be provided on the metal tools, such asby lathing, and thus transferred to the contact lens surface during thecasting process.

Having thus described the inventive concepts and a number of exemplaryembodiments, it will be apparent to those skilled in the art that theinvention may be implemented in various ways, and that modifications andimprovements will readily occur to such persons. Thus, the embodimentsare not intended to be limiting and presented by way of example only.The invention is limited only as required by the following claims andequivalents thereto.

The invention claimed is:
 1. An optical imaging arrangement, comprising:an optical imaging element for acting upon light comprising visiblewavelengths; a phase coder associated with the optical imaging element;and a dispersion coder associated with the optical imaging element, thephase coder comprising a first pattern of features that induces anon-diffractive phase effect to the light comprising visiblewavelengths, the first pattern of features comprising a first number ofoscillations between radial coordinates of 0.5 mm and 2 mm, the phasecoder providing additional depth of focus in addition to a depth offocus of the optical imaging element, the dispersion coder comprising asecond pattern of features that induces a diffractive effect to thelight comprising visible wavelengths, the second pattern of featurescomprising a second number of oscillations between radial coordinates of0.5 mm and 2 mm, the second number of oscillations being greater thanthe first number of oscillations, the dispersion coder providing focusshifts of through focus modulation transfer function (TFMTF) profilesassociated with the optical imaging element and the phase coder formultiple wavelengths of the light comprising visible wavelengths so asto increase an amount of overlap of the TFMTF profiles for the multiplewavelengths.
 2. The optical imaging arrangement of claim 1, wherein theoptical Imaging element comprises a lens.
 3. The optical imagingarrangement of claim 1, wherein the phase coder provides the additionaldepth of focus without adding optical power beyond that of the opticalimaging element.
 4. The optical imaging arrangement of claim 1, whereinthe phase coder provides the additional depth of focus without reducingan aperture of the optical imaging element.
 5. The optical imagingarrangement of claim 1, wherein the phase coder provides the additionaldepth of focus without causing loss of energy.
 6. The optical imagingarrangement of claim 1, wherein the phase coder provides the additionaldepth of focus without causing loss of resolution.
 7. The opticalimaging arrangement of claim 1, wherein the dispersion coder provideschromatic aberration correction.
 8. The optical imaging arrangement ofclaim 1, wherein the first pattern is a radial pattern and the secondpattern is a radial pattern.
 9. The optical imaging arrangement of claim1, wherein the first and second patterns are located at first and secondsur aces, respectively, of the optical imaging element.
 10. The opticalimaging arrangement of claim 1, wherein the first and second patternsare in the form of first and second surface reliefs, respectively. 11.The optical imaging arrangement of claim 1, wherein the first and secondpatterns are incorporated in the optical imaging element.
 12. Theoptical imaging arrangement of claim 1, wherein one of the first andsecond patterns is incorporated in the optical imaging element, and theother of said first and second patterns comprises a mask located at aside of the optical imaging element.
 13. The optical imaging arrangementof claim 1, wherein the first and second patterns are disposed at a samesurface and define together a combined pattern comprising asuperposition of said first and second patterns.
 14. The optical imagingarrangement of claim 1, wherein the optical imaging arrangement isconfigured as a lens.
 15. The optical imaging arrangement of claim 1,wherein the imaging arrangement is configured as an ophthalmic lens. 16.The optical imaging arrangement of claim 15, wherein the ophthalmic lensis a multi-focal lens.
 17. The optical imaging arrangement of claim 1,wherein the imaging arrangement is configured as a contact lens.
 18. Theoptical imaging arrangement of claim 17, wherein the contact lens is amulti-focal lens.
 19. The optical imaging arrangement of claim 1,wherein the optical imaging arrangement comprises multiple zones havingdifferent optical powers.
 20. The optical imaging arrangement of claim1, wherein the first pattern of features of the phase coder comprisesthree oscillations between radial coordinates of 0.5 mm and 2 mm, andwherein the second pattern of features of the dispersion coder comprisesseven oscillations between radial coordinates of 0.5 mm and 1.5 mm.